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By Yeliseyev AK, Shestakov AM

Comminution is the most power-intensive process in the technology for ferrous quartzite concentration. That is why improving comminution efficiency leads to the most appreciable economic effect on the concentration process. The trend towards reducing the lump size of crushed ore before charging the mill is considered to be of major importance in improving comminution efficiency. A considerable number of investigations have been performed in this direction. At the same time, a strong interest is also maintained in the increase of comminution efficiency due to optimisation of process taking place in the mill. Recently, investigations of the power intensity of the breaking process inside the mill have been carried out at the Krivoy Rog Mining Institute. It was ascertained that the routine conditions of comminution at a low mill ball charge ratio resulted in an unnecessarily high power consumption due to the force of impact of falling and milling bodies far exceeding the power required for comminution. For example, the power value for falling balls of 60 - 125 mm in diameter reaches 0.3 kNm, and the force and stress due to ball contact with the lining reaches 60 kN and 250 MPa respectively. These values exceed the force required for comminution by a factor of ten. Analysis of the mechanism of ore particle size reduction during comminution in the ball mill indicates that the size reduction is due to impact load, attrition load, and static load. The efficiency of size reduction is very low. During comminution in the ball mill, impact loads prevail and amount to 85 - 90 per cent of the total load. In this situation, not more than 10 - 15 per cent of destruction is due to attrition.

Jan 1, 1993

By E. R. Bauer

This report describes a U.S. Bureau of Mines investigation into the removal of gate road chain pillars in conjunction with longwall retreat mining. The research objective was to determine, through evaluations of the loads imposed on the gate road pillars and supplemental support elements in the entries, how the pillars, supplemental support, and entries were affected by the longwall abutment pressure. To achieve this goal, vibrating wire stressmeters and hydraulic flatjack pressure cells were installed in the support elements to monitor stress change caused by abutment pressure as a function of longwall face advance. The findings documented in this report are the result of information collected from instrumentation and observation at the mine. Pillar and support loading measurements and stability observations revealed that the roof and the sup- port elements remained stable during panel retreat, while the face progressed at a normal rate of advance. The ability to safely and efficiently mine chain pillars during panel retreat increases resource recovery and can provide several other benefits described in this report.

Jan 1, 1993

By B. R. Casement

"Managing safety on the basis of after-the-fact reaction to accidents, can never be more than partially successful. Injuries will occur as long as the underlying potential for them still exists. Unless unsafe actions and conditions are systematically decreased, no program can have more than a short-term success.The pro-active Bullmoose loss control process, instead, focusses on heightening awareness of work habits, to prevent incidents by reducing their potential.Any safety program will be doomed to failure if the development of safe work habits depends on the safety supervisor or a safety committee. At Bullmoose the focus is on the critical actions out of which losses emerge. The successful application of performance-related feedback is achieved by taking safety, health, and environmental concerns into consideration on every level, and, by doing the right thing in every job done.What is an Exceptional Loss Control Program?If an accident in an organization creates a flurry of interest, resulting in ""cracking down"" on violations for a short period of time then an ""exceptional"" loss control program exists. Unfortunately, exceptional here does not refer to the effectiveness of quality of the program but to the fact that the organization is managing loss control by exception. The degree of management attention in an ""exceptional"" safety program varies over a period of time, remaining low as long as the rate of losses stays within management's acceptable control limit (Fig. I). When the losses rise above this, management becomes motivated to begin ""exceptional"" efforts to manage losses. When the rate falls again to within the accepted limit, efforts to control losses take a back seat.Such a strategy guarantees that losses will be tolerated or ignored as long as the actual rate is below the acceptable limit. Simply to lower the limit would not reduce losses, but would result in an increased number of flurries of management attention to loss control. This ""on-again, off-again"" style of management teaches supervisors and others that basic loss control is not as important as are statistics."

Jan 1, 1993

By Yu. A. Polozov, V. A. Lagunov, O. Yu. Lushinkova, Yu. I. Svirskiy, Eh. Ya. Kipko, Roy A. Williams

1.1 GENERALIZED METHODS OF SUPPRESSING THE INFLOW OF GROUND WATER DURING THE CONSTRUCTION OF SHAFTS, DRIFTS AND TUNNELS Various methods are used to prevent or minimize the inflow of ground water into underground workings during their excavation. The two most common methods include freezing the saturated rock and grouting using cement, sodium silicate, polyurethane and/or other chemicals. Each of these technologies for combatting the inflow of ground water is effective only under specific hydrogeological conditions. For example, although the freezing of saturated ground is among the more universally adopted methods, it is designed to provide only temporary protection during construction. Before the saturated rock thaws it is necessary to emplace a waterproof liner which is labor intensive, time consuming, and expensive. Consequently, freezing is used only in exceptionally complex hydrogeological conditions, namely in those cases where the water-bearing strata consist of unstable rock or the ground water has an anomalous hydrochemistry. The classical grouting of saturated rock, carried out from the surface or from the face of the underground workings for the purpose of limiting the inflow of ground water during excavation, utilizes both cement and a variety of chemical grouts. Cement grouting has been regarded as the main method of combatting the inflow of ground water in fractured rock throughout the world. In such countries as the Federal Republic of Germany (FRG), Canada, the Republic of South Africa and Great Britain, cement grouting is the main method of reducing the inflow of ground water during the excavation of mine openings. In Great Britain and the FRG, cement grouting has been used in 80% of all shaft excavations. In the Republic of South Africa cement grouting has been used in almost 100% of all the shafts that have been constructed. The installation of grout curtains into permeable water- bearing strata significantly reduces their permeability and increases the rock strength. Grouting has the greatest effect in fractured sandstones, certain well indurated shales, fractured granites, fractured quartzites, and karstic limestones or dolomites. The following principal factors must be considered when assessing the expediency of grouting rock with cement: the geometry of the network of fracture openings, the saturated hydraulic conductivity of the fractured rock, the hydraulic head acting on the water in the rock, and the chemical composition of the ground water. On the basis of the geometry of the fractures and the thickness of each hydrostratigraphic unit, the characteristics of the cement grout are selected. As a rule, the cementing of large fractured zones with high ground water velocities is carried out using inert fillers (sand, mill slag, loam, loess, crushed limestone), special types of cement, setting accelerators, and high cement concentrations in water. Calcium chloride, soda ash, sodium silicate, sodium nitrate, amino alcohols, tin bichloride, trisulphate nitrate, and lumnite are used extensively as the setting accelerators for cement grouts. In the FRG and Poland, special cement injection compounds that embody a mixture of cement and active cement metal salts, water additives and binding substances are being used for the cementing of saturated zones with rapid ground water velocities. These reagents accelerate the rate of structure-forming reactions. In spite of the wide variety of additives used for cement grouts, the effectiveness of the method in large fractures below the water table is either poor or it leads to a very large consumption of cement due to the erosion of the grout through the cracks before it hardens. At the present time, a large number of cement types and brands are being produced by various countries. These variations permit cementing to be employed in a variety of geological conditions. However, both pure cement grout and grouts with fillers constitute unstable systems with a high water loss rate. Therefore during the grouting of finely fractured rock the cement grout's premature loss of a large amount of free water causes its consistency to increase, whereupon the grout solidifies. Consequently, it inadequately penetrates into the fine fractures of the stratum. In addition the high water loss rate in the cement grout causes unreacted cement particles to remain, which greatly reduces the grout hardness and the resulting rock strength characteristics are weakened. As a result, the binding properties of the cement are utilized perhaps up to 60%. The remaining portion is left in the grout as a filler. All these conditions significantly decrease the efficiency of the isolation effort both with respect to strength and cost. In order to expand the cement grouting method, re- search is being conducted to improve the quality of cement grout, to increase its range of application with respect to permeability control, to reduce its water loss rate and to increase its capacity to withstand the erosive and corrosive effects of poor quality ground water. For example, mixtures of bentonitic clay, carboxymethyl cellulose, aerated sodium sulfide, sulphated alcohol distillery waste, nitrolignin, gip-

Jan 1, 1993

By W. J. Mitchell

During the months of April and May 1992, the Phelps Dodge Hidalgo smelter underwent a major turnaround. This was the third such turnaround in the life of the facility which was commissioned in 1976. During the third furnace campaign, the smelter processed 5.2 million tons of concentrate producing 2.6 billion pounds of anode copper over a 7.5 year period. The critical path on the fifty-nine (59) day turnaround schedule was the reconstruction of the Outokumpo flash furnace which integrated some modifications with standard rebuild practices. Modifications included incorporation of horizontal cooling jackets throughout the furnace settler as well as the installation of castable refractory in the reaction and uptake shafts.

Jan 1, 1993

By Charles L. Kimbell

This study is intended to serve three roles. First, it is the second annual edition of this study in a separate volume that represents a global overview and summary to supplement and complement the five regional volumes that now constitute the U.S. Bureau of Mines international, geographically arranged studies. In this regard, it also extends previous works under this title that appeared in the inter-national volume of the Minerals Year-book from the inception of that volume (the 1963 edition) until it was subdivided into six separate volumes in 1989. Following the traditional format of past chapters under this title, the basic statistical presentations herein deal chiefly with 1990, and in a few instances with 1988 or 1989; these latter two only because more recent, comprehensive global statistics simply are not yet available owing to delays in data collection and processing in some countries and continued governmental suppression of data in others. The second role of this study is to provide an update to the coverage of events impacting on the world's mineral industry that have occurred between the end of 1990 and the preparation of this study. Inclusion of this update is almost essential because of the potential effect of some of these events on global mineral industry activities.

Jan 1, 1993

By B. Hester

Many Third World countries of Third World Africa are well-endowed with minerals, especially gold. Political and economic conditions discouraged interest by Western capital for the several decades since colonial rule. Influence from Eastern Block countries has gone and the left wing orientation widely favored by Third World countries has almost disappeared. Under International Monetary Fund influence, these countries now solicit Western finance to expand their industries. Mining is especially encouraged. The paper describes the financing of some recent developments and examines trends and opportunities in some of the more attractive countries.

Jan 1, 1993

By Dendyuk TV

The possible use of combined (flotation/magnetic separation and magnetic separation/flotation) technologies involving the new flotation reagent systems for upgrading the iron ore concentrates, low grade manganese products and beneficiation of graphite-bearing dusts from integrated iron-and-steel works has been shown. It has been found that the absence of magnetic flocculation phenomenon worsens the reverse cationic flotation of oxidised iron ore concentrates and direct flotation of low-grade manganese products which require the use of modifiers possessing the flocculating properties. The synergetic mixtures of polymers have been proposed to be used as modifiers, ie polyacrylamide (PAA) with carboxymethyl cellulose (CMC) and polyacrylamide with industrial lignosulphonates (LST)

Jan 1, 1993

By R. L. Merrifield

Cominco Snip is a 60: 40 joint venture of Cominco Ltd. and Prime Resources Group Inc. Cominco manages the operation. The mine site is located in a narrow mountain valley where Bronson Creek enters the Iskut River in Northwestern British Columbia. Access is by air only to the company's 1,500 meter airstrip. Milling at a designed feed rate of 300 tpd began on schedule in January 1991. Tonnage and gold production in the form of bullion bars from the gravity circuit and gold bearing float concentrate have exceeded design forecast. This presentation will examine many of the factors that influenced the final plant design inclusive of exploration findings, bench scale and pilot plant test results, environmental and social considerations, capital and projected operating costs and product transportation alternatives such as the operation's Hovercraft.

Jan 1, 1993

By F. N. Kissell, C. D. Litton

This study predicts the level of smoke that miners might meet while trying to escape a coal mine fire and describes how smoke would impede their safe escape. For this study, the authors assumed that miners exit through an escapeway adjacent to the burning entry, that some air would leak from the burning entry to the escapeway. The following conclusions were made: • A very low amount of air leakage to the escapeway can produce a critical level of visual obscurity from smoke. This shows that intake airways may be as susceptible to smoke visibility problems as return airways. • This critical level of smoke obscurity is reached much before a critical level of carbon monoxide is reached. • Small fires can cause a severe sensory irritation that further limits vision. Thus, reliable eye protection is very important. These results show that methods to guide miners through dense smoke will contribute greatly to saving lives during mine fires.

Jan 1, 1993

By B Moynihan

The Roa Opencast Coal Mine is situated at the north-eastern end of the Greymouth Coalfield. It lies on an eastern flank of the Paparoa Range, 16 km north-east of the town of Greymouth on the West Coast of the South Island. Road access is via a sealed road from Blackball to Roa, then by a 5.3 km all weather, gravel road, which gains 340 m in elevation from 190 m RL at Roa to a maximum height of 530 m near the opencast.

Jan 1, 1993

By Takiuchi T, Kurita M, Owada S

This paper describes the possibility of the application of flotation to the separation of monazite from xenotime and of columbite from ferberite, which have been said to be difficult with generally used physical beneficiation methods. For Malaysian monazite and xenotime samples, a great difference is observed between the flotation recoveries at pH 7.5 using 1.0 x 10-4mol/1 dodecylammonium chloride (DAC). The grade and recovery of columbite in the binary flotation with both minerals result in 85 per cent and 67 per cent in the cleaning froth and 91 per cent and 51 per cent in the re-cleaning froth, without adding any scavenging stages. For monazite samples from various localities, the flotability is dominated by the electrostatic interaction between mineral surface and collector ion using DAC as collector, but the singular decrease of flotation is observed in the sample of which the crystallinity is low and the surface structure is rugged and complex. Otherwise, ferric ion in the flotation system probably dissolved from mineral is found to activate the flotation using sodium dodecylsulfate as collector. For columbite and ferberite, the separation is judged possible at pH 3.0 using 1.0 x 10'3mo1/l sodium oleate (NaOl) from the single flotation results of each mineral. In the binary flotation, however, columbite recovery in the froth is greatly diminished below that expected. This would be because NaOl is prevented from adsorbing on the columbite surface of which the charge is transformed more negative side by the specific adsorption of the tungstate ion dissolved from ferberite.

Jan 1, 1993

By F. M. Doyle, Robert G. Robins, E. Peters

Stability diagrams for the Cu-S-H2O system have been widely applied over many years. Stability diagrams for aqueous systems generally, have been generated by computer, but with the programs for Potential-pH diagrams in particular, a common routine leads to error in multi-element systems. In this paper these errors, and some misinterpretation of diagrams are considered. In most of the published diagrams for the Cu-S-H2O system there has been no account of the sulfide complexes of copper. Here, the free energies of formation for the various species in the system have been re-evaluated for consistency, and some diagrams for the Cu-S-H2O system ( generated with the program DIASTAB Vers.5 ) are presented.

Jan 1, 1993

By Bartrop S. B

Mount Isa mine has a long history of successful exploration since discovery 70 years ago. Remaining reserves, although substantial, exist in a scheduling framework which involves long-term production from new ore sources with attendant technical risk and major capital investment. Current exploration aims to incrementally increase reserve tonnage to maintain existing production levels as well as to provide a buffer for potential start-up delays from new ore sources. Exploration also aims to increase the net present value of the operation by discovering new major orebodies around the Mount Isa and Hilton mines.

Jan 1, 1993

By Mark S. Stagg, Siskind David E

The mining industry occasionally blasts near pressurized transmission pipelines and has requested guidance on safe vibration levels and setback distances. The Bureau of Mines and the Indiana Department of Natural Resources cooperated with AMAX Coal Company on a study of coal mine overburden blasting. Five buried and pressurized 250-ft pipeline sections were specifically installed on the Minnehaha Mine highwall near Sullivan, IN for testing to failure. Four welded steel pipes ranging from 6- to 20-in diameter and one 8-in PVC water supply pipe were monitored for vibration, strain, and internal pressure for a period of 6 months while production blasting advanced up to the pipeline field. In contrast to previous studies of small-scale blasting representing construction activities, these tests involved overburden blasts of up to 2100 lb per delay in 12-1/4-in diameter holes.

Jan 1, 1993

By Ali Benbia

The paper shows results from the physical modelling of longwall excavations concentrating on the fracture pattern development above longwall panels. The modelling technique is briefly described and the detailed analysis of the fracture pattern is discussed. The physical modelling is particularly useful in visualising the caving process above longwall panels. This advantage has been exploited using the image analysis technique. Black and white pictures have been taken while the models are tested in successive stages and then enhanced and stored as binary images by scanning using an image analyser coupled with a video camera. These images are then processed using a custom C program which allows the discretization and characterisation of the fractures. This provides a valuable data base for further numerical and statistical analysis which subsequently may allow the assessment of the water inflow hazard to the workings. In this paper a sequence of different extraction thickness have been analysed using the technique mentioned above to show the effect of the extraction thickness on the fracture distribution and intensity.

Jan 1, 1993

By Lynn B. Hales, Randy A. Ynchausti

Object-oriented technologies have been developed to more closely model the way we think about the world and our natural approach to solving problems. Higher levels of abstraction, generalization and classification are benefits of an object-oriented approach. Object-oriented programming, design, and expert systems are part of this technology which is shaping the future of real-time supervisory control. Goals of real-time supervisory control systems include: minimizing variations in process operations, improving efficiency, maximizing production, and implementing procedures for starting and stopping the process. Incorporating object-oriented technology in design, development and implementation of real-time supervisory control systems provides new opportunities for these tasks. This paper discusses some of the opportunities and challenges of implementing real- time supervisory control using an object-oriented expert system for a rougher flotation circuit

Jan 1, 1993

By Kumar M. Lyer

Residence time distribution (RTD) of light and heavy liquids in a pyrometallurgical channel reactor was mathematically modeled by representing the reactor as a combination of ideal reactors. Cold model studies simulated the counter-current flow of slag and matte (or metal) with high-strength bottom gas injection. The experimental variables include flow rates, heights, density and viscosity of the two liquids; gas flow rate; injector diameter; and distance between injectors. The experiments covered a wide range, of the appropriate dimensionless parameter, including conditions in ferrous and nonferrous extractive metallurgy. Dispersion modeling studies were also carried out to determine the degree of backmixing. Results indicate that the degree of backmixing in the channel reactor for various operating conditions corresponds to that for 3-20 perfectly mixed reactors in series.

Jan 1, 1993

By Dalmijn WL, Valk HJLvd

At the Faculty of Mining and Petroleum Engineering, the Department of Raw Materials Technology, a mathematical model has been developed to predict the porosity distribution in an uniform jig bed. If the porosity distribution in an uniform jig bed is known, it is possible to correlate this to the settling velocity of particles with a density different from the density of the bed grains and thus model the stratification in a jig. For measuring the porosity distribution in the jig bed a method has been developed based on light absorption techniques.

Jan 1, 1993

By Davey KJ

Complex sulphide ores are characterised by complex texture of the valuable minerals. Any assessment of the performance of differential flotation circuits treating such ore should include analysis of the effects of poor liberation of the valuable minerals. Selected samples were taken from balanced size by size surveys of the flotation section of a concentrator treating an ore body containing fine grained galena and sphalerite in a matrix of iron sulphides which is mostly pyrite. liberation measurements were made using the QEM*SEM system on four or seven size fractions. The measurements indicated that less than 40 per cent of the galena and less than 60 per cent of the sphalerite in the flotation feed was liberated. The final concentrates were largely composed of composites of valuable minerals and iron sulphide however there was a small but significant fraction of liberated iron sulphide. Using the sized mineral flows obtained from the original balances and the liberation measurements, a satisfactory liberation balance was obtained. This enabled the effect of liberation on the flotation performance to be examined; not only for the entire circuit but also in the rougher, scavenger and cleaning sections. In the zinc circuit the effect of a regrind mill could be assessed. Recovery of galena in the lead circuit was limited by the recovery of composite lead particles. Recovery of liberated galena exceeded 95 per cent in all size fractions while the recovery of composite galena exceeded 85 per cent below 38 ¦m but fell sharply above 38 ¦m. Examination of the behaviour of the liberated and composite galena in the various sections of the lead flotation circuit revealed high recoveries of both liberated and composite galena particles in the roughing and scavenging sections but very low recoveries in the final two cleaning stages. Similar trends to those observed in the lead circuit applied in the zinc circuit although the performance of the liberated sphalerite also fell off at sizes greater than 38 pm in this case. Thus the zinc recovery was limited by the flotation of both the liberated and the composite sphalerite. The effect of regrinding was to increase the recovery of sphalerite mainly by reducing the amounts of sphalerite in less liberated sizes rather than by increasing the liberation of the sphalerite within a given size Fraction.

Jan 1, 1993